CN116783498A - Battery self-discharge detection method, circuit and equipment - Google Patents
Battery self-discharge detection method, circuit and equipment Download PDFInfo
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- CN116783498A CN116783498A CN202180092665.8A CN202180092665A CN116783498A CN 116783498 A CN116783498 A CN 116783498A CN 202180092665 A CN202180092665 A CN 202180092665A CN 116783498 A CN116783498 A CN 116783498A
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- 238000001514 detection method Methods 0.000 title claims abstract description 45
- 238000012360 testing method Methods 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims description 29
- 238000005259 measurement Methods 0.000 claims description 23
- 230000008859 change Effects 0.000 description 14
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 230000010287 polarization Effects 0.000 description 6
- 238000011161 development Methods 0.000 description 4
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- 238000004134 energy conservation Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- VVNXEADCOVSAER-UHFFFAOYSA-N lithium sodium Chemical compound [Li].[Na] VVNXEADCOVSAER-UHFFFAOYSA-N 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 230000028161 membrane depolarization Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The application provides a battery self-discharge detection method, which comprises the steps of forming a first parallel circuit by a standard battery cell and a plurality of battery cells to be detected; if the first parallel circuit reaches potential balance, respectively connecting the standard battery cell and a plurality of battery cells to be tested with a current meter in series to form a second parallel circuit; if the second parallel circuit reaches potential balance, acquiring the reading value of each current measuring meter; obtaining a standard leakage current value of the standard battery cell; according to the standard leakage current value and the reading value of each current measuring meter, the potential balance can be realized rapidly, and the efficiency of the self-discharge test of the battery is improved.
Description
The application relates to the field of batteries, in particular to a battery self-discharge detection method, a circuit and equipment.
Energy conservation and emission reduction are key to sustainable development of the automobile industry, and electric vehicles become an important component of sustainable development of the automobile industry due to the energy conservation and environmental protection advantages of the electric vehicles. For electric vehicles, battery technology is an important factor in the development of the electric vehicles.
Currently, with further widespread use of lithium ion batteries, the use of batteries is not limited to single batteries alone, but more and more applications are more prone to be presented in series and parallel battery packs. The present inventors have found that the capacity and lifetime of a battery pack are related not only to a single cell but also to the uniformity of a plurality of cells, and that there is currently no effective solution for determining the uniformity of cells.
Disclosure of Invention
In order to solve the problem that the consistency of batteries cannot be effectively determined in the prior art, the embodiment of the application provides a battery self-discharge detection method, a circuit and equipment.
In one aspect, an embodiment of the present application provides a method for detecting self-discharge of a battery, including:
the method comprises the steps that a first series circuit is formed by a standard battery cell and a first current meter, a second series circuit is formed by a battery cell to be tested and a first resistor, and the resistance values of the first current meter and the first resistor are the same;
the first serial circuit and the second serial circuit are connected in parallel to form a first parallel circuit;
if the first parallel circuit reaches potential balance, replacing the first resistor with a second current meter to form a second parallel circuit;
acquiring a read value of the first current measuring meter, a read value of the second current measuring meter and a standard leakage current value of the standard cell;
and calculating the leakage current value of the battery core to be tested according to the read value of the first current measuring meter, the read value of the second current measuring meter and the standard leakage current value, wherein the resistance values of the first current measuring meter and the second current measuring meter are the same.
According to the battery self-discharge detection method provided by the embodiment of the application, the second current meter reading value of each battery cell to be detected can be obtained quickly, the time for carrying out potential equalization on the second parallel circuit is saved, the battery cell detection efficiency is greatly improved, meanwhile, the influence of temperature change on the test is reduced by greatly reducing the resistance of the bus, and the test accuracy is improved.
In some embodiments, before the standard cell and the first current meter form a first series circuit and the cell to be tested and the first resistor form a second series circuit, the method includes: forming a third parallel circuit by the standard battery cell and the battery cell to be tested; and determining that the third parallel circuit reaches potential balance.
In this way, since the potential equalization of the third parallel circuit is performed first, the potential equalization process of the first parallel circuit is greatly accelerated when the first parallel circuit is formed, and the detection efficiency is improved.
In some embodiments, the third parallel circuit reaches potential equalization, comprising: respectively obtaining voltage values of the standard battery cell and the battery cell to be tested; and if the difference value of the voltage values is smaller than a preset first voltage threshold value, determining that the third parallel circuit reaches potential balance. In this way, it can be quickly determined whether the third parallel circuit reaches potential equalization, improving measurement efficiency.
In some embodiments, the third parallel circuit reaches potential equalization, comprising: after the standard battery cell and the battery cell to be tested form a third parallel circuit, if the running time of the third parallel circuit exceeds a first time length threshold value, determining that the third parallel circuit reaches potential balance. The potential balance of the third parallel circuit is realized in the mode, and the implementation is simple and convenient.
In some embodiments, the first parallel circuit reaches potential equalization, comprising: and acquiring a read value of a first current measurement meter connected in series with the standard battery cell, and determining that the first parallel circuit achieves potential balance if the read value variation is smaller than a preset first current threshold value. By the mode, the state of the first parallel circuit can be quickly acquired, and the measuring efficiency can be greatly improved.
In some embodiments, the first parallel circuit reaches potential equalization, comprising: and when the running time of the first parallel circuit exceeds a second time threshold, determining that the first parallel circuit reaches potential balance. The potential equalization of the first parallel circuit is realized in the mode, and the implementation is simple and convenient.
In some embodiments, the calculating the leakage current value of each to-be-measured cell according to the read value of the first current meter, the read value of the second current meter and the standard leakage current value includes: acquiring a read value of a first current meter connected in series with the standard battery cell; and summing the reading value of the first current measuring meter connected in series with the standard battery cell and the standard leakage current value, and subtracting the value of the second current measuring meter connected in series with the battery cell to be measured to obtain the leakage current value of the battery cell to be measured.
By acquiring the standard leakage current value of the standard battery cell and combining the measured values of the first current measuring meters and the second current measuring meters, the leakage current value of each battery cell to be measured can be accurately calculated, and the measurement precision and the measurement efficiency are improved.
In some embodiments, the method further comprises: and if the leakage current value of the battery cell to be tested is larger than a preset allowable leakage current threshold value, determining that the battery cell to be tested is unqualified in self-discharge.
By the mode, the battery cells with abnormal self-discharge can be rapidly screened, and the battery performance is prevented from being influenced by the combination of the battery cells with different leakage current values.
On the other hand, the embodiment of the application also provides a battery self-discharge detection circuit, which comprises: the device comprises a standard cell, a cell to be tested, a first resistor, a first current meter, a second current meter and a first selection switch;
the standard cell and the first current meter form a first series circuit;
one end of the battery cell to be tested is connected with one end of the first resistor and one end of the second current measuring meter respectively through the first selection switch; the resistance values of the first current measuring meter and the second current measuring meter are the same;
when the first selection switch is communicated with the first resistor, the battery cell to be tested and the first resistor form a second series circuit, and the first series circuit and the second series circuit form a first parallel circuit;
if the first parallel circuit achieves potential balance, the first selector switch disconnects the battery core to be tested from the first resistor, the battery core to be tested is connected with the second current meter, and the battery core to be tested and the second current meter form a third series circuit;
the first series circuit and the third series circuit form a second parallel circuit.
The battery self-discharge detection circuit provided by the embodiment of the application can quickly obtain the second current measurement meter reading value of each battery cell to be tested, saves the time for carrying out potential equalization on the second parallel circuit, greatly improves the battery cell detection efficiency, and simultaneously reduces the influence of temperature change on the test by greatly reducing the bus line resistance and improves the test accuracy.
On the other hand, the embodiment of the application also provides a battery self-discharge detection device, which comprises the battery self-discharge detection circuit in the embodiment.
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
fig. 1 shows a flowchart of a method for detecting self-discharge of a battery according to an embodiment of the present application;
FIG. 2 shows a schematic diagram of a first parallel circuit connection according to an embodiment of the present application;
fig. 3 shows a schematic diagram of a second parallel circuit connection according to an embodiment of the present application;
FIG. 4 is a graph showing experimental data of leakage current test temperature according to an embodiment of the present application;
FIG. 5 is a diagram showing experimental data for balanced leakage current test according to an embodiment of the present application;
fig. 6 shows a third parallel circuit connection schematic according to an embodiment of the present application;
fig. 7 shows a structure diagram of a battery self-discharge detection circuit according to an embodiment of the present application.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion. The terms first, second and the like in the description and in the claims or in the above-described figures, are used for distinguishing between different objects and not necessarily for describing a particular sequential or chronological order.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the described embodiments of the application may be combined with other embodiments.
In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "attached" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
The term "and/or" in the present application is merely an association relation describing the association object, and indicates that three kinds of relations may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In the present application, the character "/" generally indicates that the front and rear related objects are an or relationship.
The term "plurality" as used herein means two or more (including two), and similarly, "plural sets" means two or more (including two), and "plural sheets" means two or more (including two).
In the present application, the battery cell may include a lithium ion secondary battery, a lithium ion primary battery, a lithium sulfur battery, a sodium lithium ion battery, a sodium ion battery, a magnesium ion battery, or the like, which is not limited in the embodiment of the present application. The battery cell may be in a cylindrical shape, a flat shape, a rectangular parallelepiped shape, or other shapes, which is not limited in this embodiment of the application. The battery cells are generally classified into three types according to the packaging method: the cylindrical battery cell, the square battery cell and the soft package battery cell are not limited in this embodiment.
Currently, with the development of technology, power batteries are increasingly used. The power battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles, and the like, and a plurality of fields such as military equipment, aerospace, and the like. With the continuous expansion of the application field of the power battery, the market demand of the power battery is also continuously expanding.
The inventors found in the study that the capacity and the service life of the battery are not only related to the single battery, but also related to the consistency of the battery, the consistency of self discharge is an important part, and the self discharge size of the battery influences the whole performance of the single battery, the battery module and the electric cabinet. Therefore, in the production process, it is important to perform self-discharge consistency screening classification on the battery cells, and how to quickly judge the self-discharge is a key difficulty.
Currently, the main self-discharge screening method of lithium ion batteries is to measure the K value (OCV change with time) of the battery, namely, measure the voltage drop of the battery in unit time. Although this method can detect the self-discharge rate of the battery more effectively, it has a great disadvantage of being time-consuming. The method originates from the self-discharge detection of the lithium ion battery of the portable equipment with low capacity, the test duration is relatively acceptable, but if the method is used for detecting the large battery cells such as the power lithium ion battery and the like along with the larger capacity of the battery cells, the voltage drop in unit time is very small and is limited by the measurement accuracy of the voltage, so that the self-discharge rate can be accurately measured in a longer time.
At present, some methods based on leakage current test, such as a constant voltage source-cell method and a cell-cell parallel method, mainly determine that the compensation current or the change delta I of the current is based on the same time delta t, and along with the improvement of the capacity of the power lithium ion cell, the change delta I in a short time is smaller, and then, the application on an actual production line is considered, the change of the environment temperature is an important factor, and if the temperature change is superimposed, a longer time may be needed to determine the change difference of the leakage current. Meanwhile, the current difference value measured by the method is a relative value and is not the absolute leakage current of the battery cell, and the screening standard is difficult to formulate.
Based on the above consideration, the embodiment of the application provides a battery self-discharge detection method, a circuit and detection equipment, wherein a standard cell with a known leakage current value is connected with a detected cell, a resistor is adopted to replace an ammeter to perform potential equalization, after the potential equalization is achieved, the resistor is switched to a current measuring meter to perform current measurement, the change of a test voltage is replaced by the change of a test current, long-time standing is not needed, and the leakage current condition of each cell can be detected more accurately and intuitively. Meanwhile, by reducing the resistance of the bus line, leakage current with larger value can be achieved more rapidly, and the influence of temperature on measurement accuracy can be effectively avoided.
When the battery self-discharge detection method, the circuit and the detection equipment provided by the embodiment of the application are implemented, potential equalization and bus line resistance are two factors which have great influence on a detection result.
The potential equalization refers to the voltage equalization condition among the battery cells, if the voltage among the battery cells is in an unbalanced state, the current in the circuit is overlarge, if the current in the circuit is overlarge, larger current charge and discharge can occur among the battery cells, the polarization of the battery cells is aggravated, the polarization current is increased, the basic current of the test is increased, and the battery cells need longer time to perform depolarization operation so as to detect the real leakage current. In order to achieve the balance quickly, the electric potential among the battery cells needs to be balanced as much as possible, so that the initial current is ensured to be in a lower range, and the generation of polarization current is not enough to be caused or reduced as much as possible.
The total line resistance is the total resistance of the whole detection circuit and mainly comprises a connecting sheet resistance, a cell internal resistance, an ammeter internal resistance, a test line resistance and the like, if the total line resistance is larger, the current value in the line is lower, and if the same balance leakage current is required, longer balance time is required. Because the internal resistance of the cell and the resistance of the connecting sheet are much smaller than the internal resistance of the ammeter and the resistance of the test line, the reduction of the resistance of the bus line mainly reduces the internal resistance of the ammeter and the resistance of the test line.
Fig. 1 shows a flowchart of a method for detecting self-discharge of a battery according to an embodiment of the present application, where the method for detecting self-discharge of a battery mainly includes:
step 110: and forming a first series circuit by the standard battery cell and the first current meter, forming a second series circuit by the battery cell to be tested and the first resistor, wherein the resistance values of the first current meter and the first resistor are the same.
The standard cell is a cell with a known leakage current value, the performance of the standard cell is relatively stable, the leakage current value of the standard cell is known and can be used as a standard for measurement and comparison, and the cell stored for about 90 days is usually selected as the standard cell, and the known leakage current value is used as the standard leakage current value for comparison. Of course, other standards may be used for selecting the standard cell, as long as it has a stable standard leakage current value. The number of standard cells may be one or more, and the number is not limited.
Fig. 2 is a schematic diagram showing connection of a battery self-discharge detection circuit according to an embodiment of the present application, in which a first current meter A1 is connected to one end of a standard cell S and is connected in series with the standard cell S, and a first resistor is disposed at one end of a to-be-detected cell and forms a second series circuit with the to-be-detected cell. As shown in fig. 2, each cell to be tested forms a second series circuit with a different first resistor.
In order to reach potential equalization as soon as possible and avoid the generation of polarized current, the resistance value of the first resistor is the same as that of the first current measuring meter, and meanwhile, in order to reduce the resistance value of the total line, the connecting line is a connecting line with a smaller resistance value as far as possible.
Because the total resistance value of the circuit has a large influence on potential equalization, if the total resistance value of the circuit is too large, the potential equalization time is too long, and in the embodiment of the application, the resistance value of each first resistor is not more than 50 milliohms, under the resistance value, the potential equalization time of the first parallel circuit is greatly shortened, as shown in table 1, the time required for the circuit to reach potential equalization by selecting the first resistors with different resistance values is shown.
TABLE 1
| First resistance value of resistor | Potential equalization time |
| 1 milliohm | 1.25 hours |
| 10 milliohms | 2.5 hours |
| 100 milliohms | 20 hours |
| 1 European | 150 hours |
| 10 European style | 1750 hours |
As can be seen from Table 1, the first resistor with a resistance value not greater than 50 mOhm is selected in the embodiment of the application, so that the time for potential equalization can be greatly shortened.
Step 120: the first series circuit and the second series circuit are connected in parallel to form a first parallel circuit.
With continued reference to fig. 2, after the first current meter A1 and the standard cell S are formed into a first series circuit, the cell to be tested and the first resistor are formed into a second series circuit, and then the first series circuit and the plurality of second series circuits are connected in parallel to form a first parallel circuit. In the first parallel circuit, the cathodes of the battery cells to be tested are connected, and the anodes of the battery cells to be tested are respectively connected with the first resistor.
Step 130: if the first parallel circuit reaches potential balance, the first resistor is replaced by a second current measuring meter to form a second parallel circuit.
After the standard battery cell, the battery cell to be tested, the first current measuring meter A1 and the first resistor form a first parallel circuit, potential equalization among the battery cells is needed to reduce the influence caused by polarized current. The first parallel circuit is subjected to potential equalization in a manner of standing the first parallel circuit, for example, after the first parallel circuit is kept stand for 3-5 hours, the first parallel circuit is considered to reach potential equalization; it is also possible to determine whether the first parallel circuit reaches the potential equalization by judging the read value variation of the first current meter connected in series with the standard cell.
When the first parallel circuit reaches potential balance, the polarized current between the standard cell and each cell to be tested is considered to be minimum, and the cells are in a stable state, and the first resistor is replaced by a second current meter to form a second parallel circuit.
The second parallel circuit is shown in fig. 3, after the first parallel circuit reaches potential balance, the first current meter A1 connected with the standard cell S remains unchanged, and the first resistor connected in series with each cell to be tested is quickly replaced by the second current meter A2, a 3..a16, and the like.
Because the leakage current value of each electric core is generally smaller, in order to accurately measure the leakage current value of each electric core to be measured, the first current measuring meter and the second current measuring meter need to be high-precision current meters, for example: a current meter with an accuracy of ±1ua may be selected. Meanwhile, the resistance values of the first current measuring meter and the second current measuring meter are required to be consistent, or the resistance value difference value of the first current measuring meter and the second current measuring meter is within a certain threshold range, so that the influence on measuring accuracy caused by overlarge resistance value difference is avoided. The resistance values of the first current measuring meter, the second current measuring meter and the first resistor adopted by the embodiment of the application are the same or the resistance value difference is within a certain threshold range.
When the first resistor is replaced by the second current meter, quick switching is needed, and potential unbalance of the second parallel circuit caused by too slow switching speed is avoided. The switching is performed after the first parallel circuit reaches potential equalization, and the resistance values of the first resistor and the second current meter are the same, so that the first resistor is quickly switched into the second current meter, the potential equalization state of the original first parallel circuit is not damaged, and after the second parallel circuit is formed, the second parallel circuit can still be in the potential equalization state, thereby avoiding the influence of polarized current on the second parallel circuit.
Step 140: and acquiring the read value of the first current measuring meter, the read value of the second current measuring meter and the standard leakage current value of the standard battery cell.
After the first resistor is switched into the second current measuring meter, the second parallel circuit is still in a potential balance state, so that potential balance of the second parallel circuit is not needed, current reading values of each series circuit can be directly obtained through the first current measuring meter and the second current measuring meter, potential balance time of the second parallel circuit is saved, and the efficiency of self-discharge detection of the battery cell is greatly improved.
The current reading value of each series circuit is obtained by reading the first current measuring meter and the second current measuring meter, for example: the current meter connected with the standard cell has a reading value I s The reading values of the current measuring meter connected with the battery core to be measured are I respectively 2 ，I 3 ,I 4 ......I 15 。
Since the standard leakage current value is known when the standard cell is selected, the standard leakage current value I is directly used s-shaped drain And (3) obtaining the product.
Step 150: and calculating the leakage current value of the battery core to be measured according to the read value of the first current measuring meter, the read value of the second current measuring meter and the standard leakage current value.
Because the reading values of the first current measuring meter and the second current measuring meters are obtained when the second parallel circuit is in a potential balance state, the total current value of each series circuit is the same, namely the leakage current value of each battery cell to be measured is equal to the sum of the current values measured by the second current measuring meters corresponding to the battery cells to be measured.
Assume that the leakage current value of each cell to be tested is I 2 leak ，I 3 leak ......I 15 leak The leakage current value of each cell to be tested can be calculated by the following formula:
I s +I s-shaped drain ＝I 2 +I 2 leak ＝I 3 +I 3 leak ＝......＝I 15 +I 15 leak ；
Due to I s-shaped drain Is known, I s ，I 2 ，I 3 ,I 4 ......I 15 For the reading value measured by the first current measuring meter and the second current measuring meter, therefore, the leakage current value I of each cell to be measured can be calculated 2 leak ，I 3 leak ......I 15 leak 。
Fig. 4 shows a schematic diagram of the effect of temperature fluctuation on measurement results when leakage current is detected by the battery self-discharge detection method according to the embodiment of the application, and it can be seen from the figure that the effect of temperature variation on the leakage current value of each battery cell to be detected is very small when the temperature variation is +/-1 ℃, +/-2 ℃ and +/-3 ℃ after the first parallel circuit reaches potential equalization by adopting the method according to the embodiment of the application, and the effectiveness of the battery self-discharge detection method according to the embodiment of the application is further verified.
Fig. 5 shows the Simulink simulation result of the self-discharge detection of the battery by the self-discharge detection method provided by the application, which simulates the battery cores with different leakage currents, and when the line resistance is fixed, the change of the leakage currents and the balance time are balanced when the battery self-discharge detection method provided by the embodiment of the application is used for testing, so that the feasibility of the testing method provided by the embodiment of the application is further verified.
It can be seen from the above that, in the battery self-discharge detection method provided by the embodiment of the application, the standard battery core is connected, after the first parallel circuit composed of the standard battery core, the first current measurement meter, the battery core to be detected and the first resistor reaches the potential balance, the first resistor is switched to the second current measurement meter, so that the reading value of the second current measurement meter of each battery core to be detected can be quickly obtained, the time for potential balance of the second parallel circuit is saved, the battery core detection efficiency is greatly improved, and meanwhile, the influence of temperature change on the test is reduced by greatly reducing the bus resistance, and the test accuracy is improved.
In some embodiments, in order to achieve a better detection effect and improve detection accuracy, before forming the standard cell and the first current meter into the first series circuit and forming the cell to be detected and the first resistor into the second series circuit, the method further includes: forming a third parallel circuit by the standard battery cell and the battery cell to be tested; the third parallel circuit is determined to reach potential equalization.
As shown in fig. 6, in order to reduce the influence of the polarization current, before the standard cell and the first current meter are combined into the first series circuit and the cell to be measured and the first resistor are combined into the second series circuit, the standard cell and each cell to be measured are first subjected to potential equalization.
Fig. 6 shows a third parallel circuit formed by connecting a standard cell and a cell to be tested in parallel, and the third parallel circuit performs potential equalization between the cells to reduce the influence caused by polarization current. The third parallel circuit is subjected to potential equalization in a manner of standing the third parallel circuit, for example, after the third parallel circuit is kept stand for 12 hours, the third parallel circuit is considered to reach potential equalization; the voltage variation of the standard battery cell and each battery cell to be tested can be judged, and if the variation is smaller than a certain threshold value, the standard battery cell and each battery cell to be tested can be considered to reach potential balance. When the third parallel circuit reaches potential balance, the polarized current between the standard cell and each cell to be tested is considered to be minimum, and the cell is in a stable state, and the standard cell, the first current meter, each cell to be tested and each first resistor form the first parallel circuit.
In this way, since the potential equalization of the third parallel circuit is performed first, the potential equalization process of the first parallel circuit is greatly accelerated when the first parallel circuit is formed, and the detection efficiency is improved.
In some embodiments, determining whether the third parallel circuit reaches potential equalization includes: respectively obtaining voltage values of a standard cell and a plurality of cells to be tested; and if the difference value of the voltage values is smaller than the preset first voltage threshold value, determining that the third parallel circuit reaches potential balance.
After the standard battery cells and the battery cells to be tested form the third parallel circuit, the third parallel circuit is required to be subjected to potential equalization, so that the polarization current between the battery cells can be greatly reduced by the potential equalization, and the detection accuracy is improved.
In the embodiment of the application, whether the third parallel circuit reaches potential balance can be determined by acquiring the difference value of the voltage values between the standard cell and each cell to be tested. And measuring voltage values of both ends of the standard battery cell and both ends of each battery cell to be measured through a voltmeter, and determining that the third parallel circuit achieves potential balance when the difference value of each voltage is smaller than a preset first voltage threshold value.
In this way, it can be quickly determined whether the third parallel circuit reaches potential equalization, improving measurement efficiency.
In some embodiments, determining whether the third parallel circuit reaches the potential balance may further determine that the third parallel circuit reaches the potential balance by forming the standard cell and the plurality of cells to be tested into the third parallel circuit and then exceeding the first time threshold by the operation time of the third parallel circuit.
As an alternative to the above manner, in the embodiment of the present application, after the third parallel circuit is built, the third parallel circuit is placed statically, and when the rest operation time of the third parallel circuit exceeds the first time threshold, it is determined that the third parallel circuit reaches the potential balance. The first time length threshold is typically set to 10-12 hours. The potential balance of the third parallel circuit is realized in the mode, and the implementation is simple and convenient.
In some embodiments, determining whether the first parallel circuit reaches the potential balance may include obtaining a read value of a first current meter connected in series with the standard cell, and if the read value variation is less than a preset first current threshold, determining that the first parallel circuit reaches the potential balance.
In step 130, after the standard cell is connected in series with the first current meter and the to-be-measured cell is connected in series with the first resistor, a first parallel circuit is formed, and the first parallel circuit needs to be placed in a potential balance state. In the embodiment of the application, whether the variation of the reading value of the first current measuring meter connected in series with the standard cell is smaller than the preset first current threshold value can be judged by acquiring the reading value i of the first current measuring meter connected in series with the standard cell, and the first parallel circuit is considered to be in a potential balance state by judging whether the reading value of the first current measuring meter connected in series with the standard cell is stable, namely di/dt=0. If the first parallel circuit does not reach the potential equalization state, the first parallel circuit continues to wait for the first parallel circuit to reach the potential equalization state.
By the mode, the state of the first parallel circuit can be quickly acquired, and the measuring efficiency can be greatly improved.
In some embodiments, determining whether the first parallel circuit has reached potential equalization may be performed by determining whether the first parallel circuit run time exceeds a second duration threshold, and if so, determining that the first parallel circuit has reached potential equalization.
In an alternative to the above manner, in the embodiment of the present application, after the first parallel circuit is built, the first parallel circuit is placed statically, and when the static operation time of the first parallel circuit exceeds the first time threshold, it is determined that the first parallel circuit reaches the potential balance. The second duration threshold is typically set to 3-5 hours. The potential equalization of the first parallel circuit is realized in the mode, and the implementation is simple and convenient.
In some embodiments, calculating the leakage current value of each cell to be measured according to the read value of the first current meter, the read value of the second current meter and the standard leakage current value includes: acquiring a read value of a first current meter connected in series with a standard cell; and adding the read value of the first current measuring meter connected in series with the standard battery cell and the standard leakage current value, and subtracting the value of the second current measuring meter connected in series with the battery cell to be measured to obtain the leakage current value of each battery cell to be measured.
In step 150, the leakage current value of each to-be-measured cell needs to be calculated according to the standard leakage current value and the read values of each first current meter and each second current meter, and because the read values of each first current meter and each second current meter are obtained in the state that the second parallel circuit is in potential balance, the total current value of each series circuit is the same, that is, the sum of the leakage current value of each to-be-measured cell and the current value measured by the current meter corresponding to the to-be-measured cell is equal.
Assume that the leakage current value of each cell to be tested is I 2 leak ，I 3 leak ......I 15 leak The leakage current value of each cell to be tested can be calculated by the following formula:
I s +I s-shaped drain ＝I 2 +I 2 leak ＝I 3 +I 3 leak ＝......＝I 15 +I 15 leak ；
Due to I s-shaped drain Is known, I s ，I 2 ，I 3 ,I 4 ......I 15 For the reading value measured by each first current measuring meter and each second current measuring meter, therefore, the leakage current value I of each battery cell to be measured can be calculated 2 leak ，I 3 leak ......I 15 leak 。
By acquiring the standard leakage current value of the standard battery cell and combining the measured values of the first current measuring meters and the second current measuring meters, the leakage current value of each battery cell to be measured can be accurately calculated, and the measurement precision and the measurement efficiency are improved.
In some embodiments, after obtaining the leakage current value of each to-be-tested battery cell, judging whether the leakage current value of the to-be-tested battery cell is greater than a preset allowable leakage current threshold value, and if so, determining that the to-be-tested battery cell is unqualified in self-discharge.
The purpose of measuring the leakage current value of the battery cell is to screen unqualified battery cells to be measured, so that leakage current is avoidedThe battery cells with larger value difference are arranged together to influence the overall performance of the battery, so that after the leakage current value of each battery cell to be detected is measured, whether each battery cell to be detected is qualified or not can be judged according to a preset allowable leakage current threshold value. The allowable leakage current threshold value can be converted into the allowable maximum leakage current value I through the month self-discharge rate of each cell to be tested max If the leakage current value I of the battery cell to be tested n-drain <I max And if not, the battery cell to be tested is considered to be normal, otherwise, the battery cell is considered to be abnormal.
By the mode, the battery cells with abnormal self-discharge can be rapidly screened, and the battery performance is prevented from being influenced by the combination of the battery cells with different leakage current values.
The embodiment of the application also provides a battery self-discharge detection circuit, as shown in fig. 7, comprising: a standard cell S, a cell D to be tested, a first resistor R, a first current meter A1 and a second current meter A2, a3. a.16 and a first selection switch K1, K2.. K.16; the standard cell S and the first current meter A1 form a first series circuit; one end of the battery cell D to be tested is connected with one end of the first resistor R and one end of the second current measuring meter A2 through the first selection switch K respectively; the resistance values of the first current measuring meter A1 and the second current measuring meter A2 are the same; when the first selection switch K is communicated with the first resistor R, the battery cell D to be tested and the first resistor R form a second series circuit, and the first series circuit and the second series circuit form a first parallel circuit; if the first parallel circuit achieves potential balance, the first selection switch K disconnects the cell D to be tested from the first resistor R, the cell D to be tested is connected with the second current meter A2, and the cell D to be tested and the second current meter A2 form a third series circuit; the first series circuit and the third series circuit form a second parallel circuit.
The standard cell S is a cell with a known leakage current value, the performance of the standard cell is relatively stable, the leakage current value of the standard cell is known and can be used as a standard for measurement and comparison, and a cell stored for about 90 days is generally selected as the standard cell, and the known leakage current value is used as a standard leakage current value for comparison. Of course, other standards may be used for selecting the standard cell, as long as it has a stable standard leakage current value.
The first current meter A1 and the second current meter A2 are current meters with the same resistance, and generally high-precision current meters are adopted, for example: a current meter with an accuracy of ±1ua may be selected. Meanwhile, the resistance values of the first current measuring meter and the second current measuring meter are required to be consistent, or the resistance value difference value of the first current measuring meter and the second current measuring meter is within a certain threshold range, so that the influence on measuring accuracy caused by overlarge resistance value difference of the current measuring meters is avoided. Meanwhile, because the total resistance value of the circuit has a larger influence on potential equalization, if the total resistance value of the circuit is too large, the potential equalization time is too long, in the embodiment of the application, the resistance value of each first current measuring meter and each second current measuring meter is not more than 50 milliohms, under the resistance value, the potential equalization time of the second parallel circuit is greatly shortened, and as shown in table 1, the time required by the circuit to reach the potential equalization by using the current measuring meters with different resistance values is shown.
The control switch K1 is a single-pole two-throw switch, is respectively connected with the first current measuring meter and the anode and the cathode of the battery cell, and is used for controlling the access of the first current measuring meter. The control switch K2, K3...k 16 is a single pole, three throw switch connected to the first resistor, the second current meter, and the positive and negative poles of the cell, respectively, for switching the first resistor to the second current meter, or shorting the first resistor or the second current meter, respectively. Of course, the control switches K1, K2...k16 may also be other types of switches, such as a single pole single throw switch, and a plurality of single pole single throw switches may be provided and connected to the first resistor, the second current meter, and the like, which is not limited herein.
As shown in fig. 7, the standard cell S is connected in parallel with a plurality of cells D2, D3..d 16 to be tested, one end of each cell to be tested is connected in series with a current meter A2, a 3..a 16, a first resistor R2, R3..r 16, both ends of the first current meter and the second current meter are connected to both ends of a control switch K, K1 is disposed at both ends of A1, K2 is disposed at both ends of A2 and R2..k 16 is disposed at both ends of a16 and R16.
According to the circuit structure, when the leakage current of each cell to be detected is detected by the battery self-discharge detection circuit, each control switch K1, K2, K16 is contacted with the contact point 1, and when the control switch is placed at the contact point 1, each current meter and the first resistor are directly short-circuited, and the positive electrode and the negative electrode of each cell are connected to form a third parallel circuit.
When the third parallel circuit reaches a potential balance state, the control switch K1 is turned on, and meanwhile, each control switch K2, the first resistor and each battery core to be tested are connected in series to form a first parallel circuit when the control switch K16 is placed at the contact point 2.
When the first parallel circuit reaches a potential balance state, the control switches K1, K2...k 16 are placed at the contact point 3, and then the current measurement meters A1, A2, a 3..a 16 are connected in series with the standard battery cells and the battery cells to be tested to form a second parallel circuit.
When the second parallel circuit reaches a potential balance state, reading the reading values of the current measurement meters A1, A2 and A3.
According to the battery self-discharge test circuit provided by the embodiment of the application, the standard battery core is connected, after the first parallel circuit consisting of the standard battery core, the first current measurement meter, the battery core to be tested and the first resistor reaches potential balance, the first resistor is switched into the second current measurement meter, so that the reading value of the second current measurement meter of each battery core to be tested can be quickly obtained, the potential balance time of the second parallel circuit is saved, the battery core detection efficiency is greatly improved, and meanwhile, the influence of temperature change on the test is reduced by greatly reducing the resistance of the bus circuit, and the test accuracy is improved.
Some embodiments of the present application further provide a battery self-discharge detection apparatus, including a battery self-discharge detection circuit in the above embodiments, where the battery self-discharge detection circuit includes: a standard cell S, a cell D to be tested, a first resistor R, a first current meter A1 and a second current meter A2, a3. a.16 and a first selection switch K1, K2.. K.16; the standard cell S and the first current meter A1 form a first series circuit; one end of the battery cell D to be tested is connected with one end of the first resistor R and one end of the second current measuring meter A2 through the first selection switch K respectively; the resistance values of the first current measuring meter A1 and the second current measuring meter A2 are the same; when the first selection switch K is communicated with the first resistor R, the battery cell D to be tested and the first resistor R form a second series circuit, and the first series circuit and the second series circuit form a first parallel circuit; if the first parallel circuit achieves potential balance, the first selection switch K disconnects the cell D to be tested from the first resistor R, the cell D to be tested is connected with the second current meter A2, and the cell D to be tested and the second current meter A2 form a third series circuit; the first series circuit and the third series circuit form a second parallel circuit.
The battery self-discharge detection equipment provided by the embodiment of the application can quickly realize potential equalization, improves the efficiency of battery self-discharge test, and simultaneously reduces the influence of temperature change on the test and improves the accuracy of the test by greatly reducing the resistance of the bus.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may be modified or some technical features may be replaced with others, which may not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (10)
- A battery self-discharge detection method, comprising:the method comprises the steps that a first series circuit is formed by a standard battery cell and a first current meter, a second series circuit is formed by a battery cell to be tested and a first resistor, and the resistance values of the first current meter and the first resistor are the same;the first serial circuit and the second serial circuit are connected in parallel to form a first parallel circuit;if the first parallel circuit reaches potential balance, replacing the first resistor with a second current meter to form a second parallel circuit;acquiring a read value of the first current measuring meter, a read value of the second current measuring meter and a standard leakage current value of the standard cell;and calculating the leakage current value of the battery core to be tested according to the read value of the first current measuring meter, the read value of the second current measuring meter and the standard leakage current value, wherein the resistance values of the first current measuring meter and the second current measuring meter are the same.
- The method of claim 1, wherein the standard cell and the first current meter are formed into a first series circuit and the cell to be tested and the first resistor are formed into a second series circuit, and further comprising:forming a third parallel circuit by the standard battery cell and the battery cell to be tested;and determining that the third parallel circuit reaches potential balance.
- The method of claim 2, wherein the third parallel circuit reaches potential equalization, comprising:respectively obtaining voltage values of the standard battery cell and the battery cell to be tested;and if the difference value of the voltage values is smaller than a preset first voltage threshold value, determining that the third parallel circuit reaches potential balance.
- The method of claim 2, wherein the third parallel circuit reaches potential equalization, comprising:after the standard battery cell and the battery cell to be tested form a third parallel circuit, if the running time of the third parallel circuit exceeds a first time length threshold value, determining that the third parallel circuit reaches potential balance.
- The method of claim 3 or 4, wherein the first parallel circuit reaches potential equalization, comprising:and acquiring a read value of a first current measurement meter connected in series with the standard battery cell, and determining that the first parallel circuit achieves potential balance if the read value variation is smaller than a preset first current threshold value.
- The method of claim 3 or 4, wherein the first parallel circuit reaches potential equalization, comprising:and when the running time of the first parallel circuit exceeds a second time threshold, determining that the first parallel circuit reaches potential balance.
- The method of any of claims 1-6, wherein calculating the leakage current value for each of the cells under test based on the read value of the first current meter, the read value of the second current meter, and the standard leakage current value comprises:acquiring a read value of a first current meter connected in series with the standard battery cell;and summing the reading value of the first current measuring meter connected in series with the standard battery cell and the standard leakage current value, and subtracting the value of the second current measuring meter connected in series with the battery cell to be measured to obtain the leakage current value of the battery cell to be measured.
- The method of claim 7, wherein the method further comprises:and if the leakage current value of the battery cell to be tested is larger than a preset allowable leakage current threshold value, determining that the battery cell to be tested is unqualified in self-discharge.
- A battery self-discharge detection circuit, comprising: the device comprises a standard cell, a cell to be tested, a first resistor, a first current meter, a second current meter and a first selection switch;the standard cell and the first current meter form a first series circuit;one end of the battery cell to be tested is connected with one end of the first resistor and one end of the second current measuring meter respectively through the first selection switch; the resistance values of the first current measuring meter and the second current measuring meter are the same;when the first selection switch is communicated with the first resistor, the battery cell to be tested and the first resistor form a second series circuit, and the first series circuit and the second series circuit form a first parallel circuit;if the first parallel circuit achieves potential balance, the first selector switch disconnects the battery core to be tested from the first resistor, the battery core to be tested is connected with the second current meter, and the battery core to be tested and the second current meter form a third series circuit;the first series circuit and the third series circuit form a second parallel circuit.
- A battery self-discharge detection apparatus comprising the battery self-discharge detection circuit according to claim 9.
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| CN117134012B (en) * | 2023-10-26 | 2024-01-16 | 河南锂动电源有限公司 | Fault self-detection lithium battery |
| CN117347887B (en) * | 2023-12-04 | 2024-04-12 | 宁德时代新能源科技股份有限公司 | Method, system and device for testing self-discharge of battery |
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| CN102901932B (en) * | 2012-09-24 | 2014-11-12 | 合肥国轩高科动力能源股份公司 | Process for detecting self-discharge of lithium batteries |
| CN102901931B (en) * | 2012-09-24 | 2015-01-07 | 合肥国轩高科动力能源股份公司 | Method for screening lithium batteries with abnormal self discharge |
| EP3323184B1 (en) * | 2015-07-14 | 2020-01-29 | Volvo Truck Corporation | A method and system for balancing a battery pack |
| CN110935655B (en) * | 2019-11-15 | 2021-12-14 | 上海理工大学 | Self-discharge rapid screening method based on branch current change of parallel battery pack |
| CN111965545A (en) * | 2020-07-31 | 2020-11-20 | 蜂巢能源科技有限公司 | Lithium battery self-discharge detection method, device and system |
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